The invention relates to an apparatus and a method for processing tissue samples. The apparatus comprises at least one retort for accommodating the tissue samples and at least one container for storing a process medium. The container communicates with the retort depending on an operating position of a valve.
Biological tissue samples, in particular histological tissue samples, are often needed in the field of human medicine and veterinary medicine, in particular as a microscopic preparation for the assessment of cells and their surroundings. For the microscopic examination, thin sections of the tissue sample have to be prepared, which are assessed by an expert in incident light or in transmitted light under the microscope.
For preparing thin sections, for example with the aid of a microtome, the tissue sample must have a certain solidity so that thin transparent sections having a thickness in the micrometer range can be prepared with the aid of a knife. To this end, the tissue sample first has to go through a treatment process in which it is fixed, dehydrated, cleared and then infiltrated with a carrier material, preferably molten paraffin. Often, these processes are successively performed in one single apparatus, the so-called tissue processor, which, to this end, includes a closable process chamber, called retort, which accommodates the different reagents for performing the process steps at a suitable temperature and pressure.
An important process step in this connection is the infiltration of the tissue sample with the carrier material in order to stabilize and solidify the tissue sample. Prior to this infiltration process step, the clearing step is performed in which alcohol residuals still present from the dehydration step are removed. As a chemical solution for this clearing step xylene or a similar agent is used. In the subsequent infiltration step, in which the tissue sample is exposed to the carrier material, usually molten paraffin, still remaining xylene components are flushed out and absorbed by the liquid carrier material, as a result whereof the carrier material is contaminated in the retort. In the same way, residual dehydrating reagents are removed in the clearing step. Constituents dissolved out of the tissue sample itself can likewise contaminate the dehydrating reagents, the clearing reagents or the carrier material. Therefore, it is necessary that the individual process steps are divided into several partial process steps, in which the tissue sample is successively exposed to different reagents with increasing purity level within the use of one reagent.
When, for example, the infiltration process is divided into three process steps, then the tissue sample is first treated with a first carrier material which may have a relatively high contamination degree, for example, contaminated with xylene. Thereafter, a second infiltration step with a second carrier material is performed which has a higher purity level than the first carrier material. Finally, the tissue sample is exposed to a third carrier material having the highest purity level, wherein the carrier materials may comprise xylene or further reagents. In this way, the tissue sample is completely infiltrated with carrier material in a step-wise process with increasing purity level of the carrier material used for the treatment, the carrier material having sufficiently high quality for preparing a good thin section in a microtome and for a microscopic preparation.
The use of several liquid reagents with different purity levels makes it necessary that these reagents are kept ready in containers in a liquid state. When one of the reagents is contaminated too much, mostly this applies to the mentioned first reagent, then this reagent has to be replaced by a reagent having an improved purity level.